So why do we care about a "little black spot on the Sun" today or any day? Astronomers were able to figure out the size of our Solar System (mainly) by using simple geometry in the 18th century while observing the transit from different areas on Earth.
The Kepler spacecraft is currently looking for extrasolar worlds using the same transit methods used to study Venus. So far Kepler has discovered over 800 planets orbiting other stars. Earth-like worlds discovered in an earth-like orbit around other stars? Not just yet but stay tuned.
Solar filters were hand-built to fit the telesopes for safe viewing. Glasses were surprising cheap to buy online (click here for website - highly recommended for the next total solar eclipse in North America 2017!).